Body Weight Gain Is Associated with the Disease Stage in Advanced Amyotrophic Lateral Sclerosis with Invasive Ventilation

We investigated the incidence of weight gain and its related factors in patients with amyotrophic lateral sclerosis (ALS) who underwent tracheostomy and invasive ventilation (TIV). Seventy-eight patients with ALS and TIV were enrolled and followed up prospectively. We clarified the clinical profiles of patients with increased weight following TIV and examined chronological variations in their body mass index (BMI), energy intake, and serum albumin levels. Post follow-up, we determined their disease stage according to their communication impairment (stage I to V) and investigated factors associated with BMI increase following TIV. Patients with a post-TIV BMI increase ≥1.86 kg/m2 demonstrated a higher incidence of ophthalmoplegia (76.2%), total quadriplegia (61.9%), severe communication impairment (stage V; 33.3%), and hypoalbuminemia than those with a BMI increase <1.86 kg/m2. Patients with stage V communication impairment exhibited a larger and faster BMI decrease before TIV (mean −4.2 kg/m2 and −2.5 kg/m2/year, respectively); a larger BMI increase (mean +4.6 kg/m2) following TIV, despite lower energy intake; and lower albumin levels post follow-up than those with lower-stage communication impairment. Multilevel linear regression analysis demonstrated an independent association between communication impairment stages (stage V) and a post-TIV BMI increase (p = 0.030). Weight gain and hypoalbuminemia during TIV in patients with ALS were associated with the disease stage and may be attributable to the neurodegenerative processes that are peculiar to ALS.


Introduction
Amyotrophic lateral sclerosis (ALS) exhibits a deteriorating disease course resulting in respiratory muscle paralysis, eventually leading to death or the utilization of mechanical ventilation for survival. In Japan, the median ventilation-free survival time of patients with ALS is 4 years [1]. However, non-invasive and invasive ventilation can extend the survival time; a recent national surveillance report in Japan demonstrated that tracheostomy and invasive ventilation (TIV) prolonged the survival time by more than 10 years in patients with ALS [2].
Researchers have identified several prognostic factors for survival in patients with ALS, upon determining death or tracheostomy as the endpoints. These factors include the age at onset; body region affected at onset; diagnostic delay from onset; progression Table 1 outlines the clinical characteristics of the enrolled 78 patients with ALS. In the total cohort of patients, there was a significant decrease in BMI at the time of TIV initiation compared with that at diagnosis and a significant increase at the end of follow-up compared with that at TIV initiation. The average increase in BMI following TIV was 1.86 kg/m 2 ; thus, we first classified the patients into two groups: those with a post-TIV BMI increase <1.86 kg/m 2 and with an increase ≥1.86 kg/m 2 . A comparison of both groups indicated a similar BMI at diagnosis. However, in the group with post-TIV BMI increase ≥1.86 kg/m 2 , the BMI at TIV use was lower, and the BMI difference from diagnosis to TIV use tended to be larger than in the group with an increase <1.86 kg/m 2 . The annual increase rate of BMI (∆BMI; see the Methods) after TIV use to the end of follow-up was also larger in the group with a post-TIV increase ≥1.86 kg/m 2 . Energy intake at TIV use and the end of follow-up was similar between both groups. However, the serum albumin levels were lower in the group with a post-TIV increase ≥1.86 kg/m 2 . The incidence of ophthalmoplegia and communication impairment was higher in the group with a post-TIV BMI increase ≥1.86 kg/m 2 (Table 1). Table 2 summarizes the incidence of non-motor manifestations following TIV use. The group with a post-TIV BMI increase ≥1.86 kg/m 2 displayed a higher incidence of dysuria compared with the group with an increase <1.86 kg/m 2 , thereby necessitating a urinary catheter insertion.  Pre-and post-TIV BMI differences were not correlated with the length of time from diagnosis to TIV use (p = 0.9537 and p = 0.2218, respectively; Figure 1a,b). However, preand post-TIV ∆BMI were correlated with the length of time from the diagnosis to TIV use (p < 0.0001 and p = 0.0151, respectively; Figure 1c,d): The shorter the time until TIV use, the greater rate of decrease and increase in pre-and post-TIV BMI, respectively. Post-TIV BMI difference and post-TIV ∆BMI were negatively correlated with BMI at TIV use (p < 0.0001 and p = 0.0486, respectively; Figure 1e,f): The lower the BMI at TIV use, the greater the post-TIV BMI increase and the rate of BMI increase. We did not observe significant correlations between the duration of TIV and BMI at the end of follow-up (p = 0.2182), post-TIV BMI difference (p = 0.3325), or post-TIV ∆BMI (p = 0.6664).     (Figure 2a,b). Moreover, they exhibited the lowest BMI at TIV use (Figure 3a), the largest BMI at the end of follow-up (Figure 3b), a tendency of substantial BMI decrease before TIV use (Figure 3c), the largest BMI increase after TIV use (Figure 3d), the highest rate of BMI decrease before TIV (Figure 3e), and a tendency of high rate of BMI increase after TIV use (Figure 3f).  (Figure 2a,b). Moreover, they exhibited the lowest BMI at TIV use (Figure 3a), the largest BMI at the end of follow-up (Figure 3b), a tendency of substantial BMI decrease before TIV use (Figure 3c), the largest BMI increase after TIV use (Figure 3d), the highest rate of BMI decrease before TIV (Figure 3e), and a tendency of high rate of BMI increase after TIV use (Figure 3f). The multilevel linear regression analysis suggested that the BMI at TIV use and stage V communication impairment exerted independent significant effects on the BMI variation (coefficient 0.584, 95% CI 0.320-0.848, p < 0.0001, d = 0.403; Table 3). The coefficient results indicated that low BMI at TIV use and advanced communication stage were associated with increased BMI after TIV use. In particular, stage V communication impairment exerted a different effect on BMI increase compared to the other stages (coefficient 1.469, 95% CI 0.142-2.789, p = 0.030, d = 1.014; Table 3), indicating a significant association between BMI increase and disease progression following TIV.

Results
Energy intake at TIV use did not differ between the stages ( Figure 4a); however, patients who reached stage V had the lowest energy intake at the end of follow-up ( Figure  4b). Serum albumin levels at TIV use did not differ between the stages ( Figure 4c); nonetheless, patients with stage V communication impairment displayed the lowest serum albumin levels at the end of follow-up (Figure 4d). At the end of follow-up, there were no significant correlations between serum albumin levels and BMI (p = 0.1243), and between albumin levels and energy intake (p = 0.0902). The multilevel linear regression analysis suggested that the BMI at TIV use and stage V communication impairment exerted independent significant effects on the BMI variation (coefficient 0.584, 95% CI 0.320-0.848, p < 0.0001, d = 0.403; Table 3). The coefficient results indicated that low BMI at TIV use and advanced communication stage were associated with increased BMI after TIV use. In particular, stage V communication impairment exerted a different effect on BMI increase compared to the other stages (coefficient 1.469, 95% CI 0.142-2.789, p = 0.030, d = 1.014; Table 3), indicating a significant association between BMI increase and disease progression following TIV.

Discussion
This study investigated body weight variation during long-term TIV use, and its relationship with disease stage (communication impairment). Our findings revealed that body weight in patients with ALS increased during long-term TIV use. We also observed that weight gain following TIV was associated with an initial weight loss before TIV and the disease stage (communication impairment) during TIV use. Patients who developed the most severe communication impairment (totally locked-in state) during TIV displayed Energy intake at TIV use did not differ between the stages ( Figure 4a); however, patients who reached stage V had the lowest energy intake at the end of follow-up ( Figure 4b).
Serum albumin levels at TIV use did not differ between the stages ( Figure 4c); nonetheless, patients with stage V communication impairment displayed the lowest serum albumin levels at the end of follow-up (Figure 4d). At the end of follow-up, there were no significant correlations between serum albumin levels and BMI (p = 0.1243), and between albumin levels and energy intake (p = 0.0902).

Discussion
This study investigated body weight variation during long-term TIV use, and its relationship with disease stage (communication impairment). Our findings revealed that body weight in patients with ALS increased during long-term TIV use. We also observed that weight gain following TIV was associated with an initial weight loss before TIV and the disease stage (communication impairment) during TIV use. Patients who developed the most severe communication impairment (totally locked-in state) during TIV displayed a rapid progressive weight decline until TIV, the lowest BMI at TIV use, and the largest weight gain at the advanced stage of TIV use. Notably, these patients had low energy intake and serum albumin, despite a large weight gain.
Since the skeletal muscles in patients with ALS during a long-term TIV are considered to be almost completely destroyed, the main component of the weight gain might be fat. Previous studies of energy metabolism in ALS patients reported markedly low energy expenditure in those using TIV (700 to 1000 kcal/day), indicating "hypometabolism" [13,14], which might lead to fat accumulation and weight gain. In this study, patients with the most advanced stage of communication impairment (stage V) received the lowest energy intake. However, they showed the largest increase in weight, suggesting that weight gain is pathognomonic to ALS and is related to central metabolic dysregulation.
Weight loss in the early stage of ALS is an independent prognostic factor for short survival time [4,5], and hypermetabolism specific to ALS has been suggested as weight loss pathophysiology. Metabolic analyses using indirect calorimetry [7][8][9] and the doubly labeled water method [15,16] have revealed hypermetabolism in approximately 40%-50% of patients with ALS. Furthermore, the involvement of the hypothalamus has been debated as an etiological lesion for weight loss through radiological [17,18], biochemical [19], pharmacokinetical [20,21], and neuropathological investigations [17,19,22]. The presence of TDP-43 protein inclusions in the hypothalamus suggests that ALS is a multisystem neurodegenerative disorder involving the central autonomic or metabolic nervous system [19,[22][23][24].
The effects of degenerative lesions in the hypothalamus may emerge as metabolic or autonomic symptoms in the advanced stages of TIV. We observed a significant association between weight gain and dysuria in this study, suggesting a dysfunction of the central autonomic system. A previous study using indirect calorimetry in ALS reported that patients with a totally locked-in state (stage V) demonstrated a complete loss of reactive energy consumption following enteral feeding [14], suggesting a malfunction of the central metabolic regulation system. In agreement with these findings, weight gain in advanced stages can be the outcome of ALS-related central metabolic or autonomic dysregulation. We hypothesize that the central metabolic dysregulation in ALS induces "hypermetabolism" with weight loss in the early stage and "hypometabolism" with weight gain in the advanced stage of patients using TIV. Hypometabolism may lead to previously reported manifestations in advanced ALS, such as visceral fat accumulation [25], macroglossia [26], hyperosmolar hyperglycemic state [27], hypertensive attack [28], and hypothermia [29].
Hypoalbuminemia in patients with stage V disease may be attributed to multifactorial causes, such as low energy intake, long-term immobilization, and a fatty liver. However, patients with stage V ALS displayed an increased weight compared to those in the earlier stages. Furthermore, liver function test results are usually normal in patients with ALS (data not shown), with similar immobilization states between patients with stage V and those with other stages. There were no correlations between serum albumin levels and BMI or energy intake at the end of follow-up. Hence, hypoalbuminemia was possibly associated with centrally derived hypometabolism. Patients with advanced stage ALS using long-term TIV displayed an almost complete loss of skeletal muscles. Protein metabolism might also be disrupted at this stage. Furthermore, metabolic dysregulation in ALS includes a fuel shift from glucose to lipid utilization [8,30], suggesting lipids are the primary energy source in patients with advanced-stage ALS with hypoalbuminemia.
The first limitation of this study was the small sample size. Generally, the number of patients with ALS who desire to use TIV is limited. In Japan, approximately 20% of patients with ALS use TIV [2]. The 78 patients enrolled in our study might correspond to 400 patients as a background population of ALS patients; therefore, the sample size appears sufficient for studying patients with advanced ALS using TIV. The second limitation was the lack of data on total or resting energy expenditure and the volume of fat and fat-free mass, which warranted the evaluation of fat accumulation and its relationship to BMI. The third limitation was the lack of data on metabolites related to glucose and lipid metabolism. These data would contribute to the elucidation of the fuel shift in advanced ALS. Fourthly, we should explore autonomic nervous function during TIV use to elucidate the mechanism of hypometabolism. Figure 5 shows the hypothetical schema of weight variations of patients with ALS, classified according to the stage of communication impairment. Weight variations through clinical courses of ALS might be determined by the pathophysiology of ALS and disease progression in individual patients. Weight gain under TIV induces fat accumulation and should not be interpreted as disease stability. Clinicians usually reduce energy intake in response to progressive weight gain, resulting in malnutrition and susceptibility to infections. The reduction of energy intake to <700 kcal/day also creates an ethical issue. Appropriate nutritional therapy must be established in the future for patients with advanced ALS using TIV.
metabolism. These data would contribute to the elucidation of the fuel shift in advan ALS. Fourthly, we should explore autonomic nervous function during TIV use to e date the mechanism of hypometabolism. Figure 5 shows the hypothetical schema of weight variations of patients with A classified according to the stage of communication impairment. Weight variat through clinical courses of ALS might be determined by the pathophysiology of ALS disease progression in individual patients. Weight gain under TIV induces fat accum tion and should not be interpreted as disease stability. Clinicians usually reduce en intake in response to progressive weight gain, resulting in malnutrition and susceptib to infections. The reduction of energy intake to < 700 kcal/day also creates an ethical is Appropriate nutritional therapy must be established in the future for patients with vanced ALS using TIV.

Patients
A total of 90 patients with sporadic or familial ALS or progressive muscular atro (PMA) were enrolled in the single-center, prospective observational study. The diagn of ALS was based on the revised El Escorial criteria, and patients with "clinically defin "clinically probable," "clinically probable laboratory supported," or "clinically possi ALS were included [31]. We also included patients with PMA who showed no upper tor neuron signs, as PMA is considered to be equivalent to ALS [32,33]. All patients derwent TIV and were regularly followed up via home visits or regular admission to Tokyo Metropolitan Neurological Hospital, Tokyo, Japan, between 2005 and 2017. W cluded patients who had already been using TIV before 2005 and those who began u TIV after 2005. Of the 90 patients, we excluded 12 patients during the follow-up du incomplete assessment and lack of sufficient clinical information, especially body we value. We eventually enrolled 78 patients ( Figure 6); 4 patients had a family histor ALS, whereas 3 patients had superoxide dismutase 1 gene variants. We evaluated A related genes only when the examination was possible, owing to clinical implications consent provision by the patients or their families. All patients manifested a persistent progressive disease course both before and after TIV use, besides displaying se

Patients
A total of 90 patients with sporadic or familial ALS or progressive muscular atrophy (PMA) were enrolled in the single-center, prospective observational study. The diagnosis of ALS was based on the revised El Escorial criteria, and patients with "clinically definite", "clinically probable", "clinically probable laboratory supported", or "clinically possible" ALS were included [31]. We also included patients with PMA who showed no upper motor neuron signs, as PMA is considered to be equivalent to ALS [32,33]. All patients underwent TIV and were regularly followed up via home visits or regular admission to the Tokyo Metropolitan Neurological Hospital, Tokyo, Japan, between 2005 and 2017. We included patients who had already been using TIV before 2005 and those who began using TIV after 2005. Of the 90 patients, we excluded 12 patients during the follow-up due to incomplete assessment and lack of sufficient clinical information, especially body weight value. We eventually enrolled 78 patients ( Figure 6); 4 patients had a family history of ALS, whereas 3 patients had superoxide dismutase 1 gene variants. We evaluated ALS-related genes only when the examination was possible, owing to clinical implications and consent provision by the patients or their families. All patients manifested a persistent and progressive disease course both before and after TIV use, besides displaying severe generalized muscle atrophy of the extremities and tongue. No other diseases affecting the nervous system were identified during follow-up. 35 patients died during follow-up, and 6 patients were transferred to other hospitals ( Figure 6). The follow-up lasted until December 2019, and 37 patients were alive at the end of the study. generalized muscle atrophy of the extremities and tongue. No other diseases affecting the nervous system were identified during follow-up. 35 patients died during follow-up, and 6 patients were transferred to other hospitals ( Figure 6). The follow-up lasted until December 2019, and 37 patients were alive at the end of the study.

Assessment
We designed the study to answer the following three questions: (1) do patients with ALS show significant weight gain during long-term TIV use; (2) are there differences in clinical findings, including motor and non-motor deficits, between patients with larger and smaller weight gain; (3) what are the correlative factors of weight gain during TIV use, particularly when focusing on weight changes, communication ability, and serum albumin levels before and after TIV use?
Neurologists and nurses evaluated the neurological status, functional motor deficits, nutritional state, and communication ability (communication impairment stage) of patients with ALS during home visits or regular admission to our hospital. Clinical data before 2005 were retrospectively collected from the medical database for patients who had been using TIV before the study. None of the 78 patients exhibited obvious dementia during routine neurological examinations throughout follow-up.
For each patient, we evaluated the following factors: sex, the age at onset, the body region affected at onset, height (m), length of time (years) from the onset to initiation of TIV, and length of time (years) from TIV to the end of follow-up or death. To assess nutritional status, we evaluated the body weight (kg) at the time of diagnosis, at TIV initiation, and at the end of follow-up (final evaluation). Furthermore, we calculated the annual rate of BMI variation (∆BMI, kg/m 2 /year) from diagnosis to TIV use, and from TIV use to the final evaluation time or death [6,12]. The definitions of each BMI parameter are as follows: • Pre-TIV BMI difference (kg/m 2 ) = BMI at TIV use − BMI at diagnosis; Transfered to other hospital n = 6 Alive at the end of the study n = 37

Assessment
We designed the study to answer the following three questions: (1) do patients with ALS show significant weight gain during long-term TIV use; (2) are there differences in clinical findings, including motor and non-motor deficits, between patients with larger and smaller weight gain; (3) what are the correlative factors of weight gain during TIV use, particularly when focusing on weight changes, communication ability, and serum albumin levels before and after TIV use?
Neurologists and nurses evaluated the neurological status, functional motor deficits, nutritional state, and communication ability (communication impairment stage) of patients with ALS during home visits or regular admission to our hospital. Clinical data before 2005 were retrospectively collected from the medical database for patients who had been using TIV before the study. None of the 78 patients exhibited obvious dementia during routine neurological examinations throughout follow-up.
For each patient, we evaluated the following factors: sex, the age at onset, the body region affected at onset, height (m), length of time (years) from the onset to initiation of TIV, and length of time (years) from TIV to the end of follow-up or death. To assess nutritional status, we evaluated the body weight (kg) at the time of diagnosis, at TIV initiation, and at the end of follow-up (final evaluation). Furthermore, we calculated the annual rate of BMI variation (∆BMI, kg/m 2 /year) from diagnosis to TIV use, and from TIV use to the final evaluation time or death [6,12]. The definitions of each BMI parameter are as follows: We also assessed the length of time from the onset to the initiation of enteral nutrition via nasogastric or gastrostomy tube, and the total duration of enteral nutrition until final evaluation time or death. Energy intake (kcal/day) via the feeding tube and serum albumin levels (g/dL) were also evaluated at TIV initiation and at the final evaluation time.
We determined communication ability to assess disease progression following the initiation of TIV [11,34]. The communication stage was defined using an augmentative and alternative communication device and was classified into five stages as follows: Stage I, communicated using sentences; stage II, one-word answers only; stage III, non-verbal yes/no responses; stage IV, occasional non-verbal yes/no response; and stage V, unable to communicate by any means. This staging method can be easily applied to patients with TIV and severely deteriorating motor functions that cannot be entirely assessed using conventional grading scales, such as the revised ALS functional rating scale (ALSFRS-R) [35]. Stage V corresponds to a totally locked-in state, characterized by the loss of voluntary movements, including ocular movements [11,36]. The communication stage was prospectively and regularly assessed at least every 3 months following TIV initiation. In addition, we compared the nutritional parameters, including BMI, ∆BMI, and serum albumin level, between the three subgroups classified by the communication stage at the final evaluation time (stage I, II-IV, and V).
Furthermore, we evaluated other motor disabilities, namely obvious oculomotor limitations and total quadriplegia. Obvious oculomotor limitations (ophthalmoplegia) were defined as persistent abnormal ocular movements during a bedside examination by at least two neurologists [11]. The evaluation of ocular movements included examinations of slow pursuit movement and ocular saccade speed with the vertical and horizontal gaze. Vertical ophthalmoplegia and slow saccade (slow eye movement) were the most common abnormalities [37,38]. Total quadriplegia indicated a failure to demonstrate visible muscle movements of the limbs. We defined the development period of the manifestations mentioned above during the follow-up for each patient [12].
We investigated the incidence of non-motor manifestations during follow-up, namely macroglossia, unstable blood pressure, hypothermia, dysuria (urinary catheter placement), and hyperglycemic state [27]. Macroglossia in patients with advanced ALS has been previously described [24,39]. We defined it as a condition characterized by the enlargement of the tongue and its constant protrusion over the dentition. Moreover, the patient could not volitionally retract the tongue into the oral cavity. Unstable blood pressure was defined as paroxysmal hypertension with a systolic blood pressure >180 mmHg, often accompanied by tachycardia (>100 bpm), which might result from central sympathetic hyperactivity [26]. Nocturnal hypotension occasionally followed daytime hypertension, whereas hypertensive attacks usually lasted for days or weeks and often recurred [26]. Hypothermia was defined as a constant body temperature <36 • C [27]. Dysuria indicated voiding difficulties that necessitated the insertion of a urinary catheter. Its causes (pelvic floor muscle weakness or neurogenic bladder) were not completely identified; however, we virtually accepted any reason for the performance of urinary catheterization in individual patients [27]. A hyperglycemic state was defined as an episode of paroxysmal hyperglycemia with a blood glucose level >400 mg/dL [25].

Statistical Analysis
We performed Welch's t-test or chi-square test for data comparison between the two groups (patients with BMI increase ≥1.86 kg/m 2 and those with BMI increase <1.86 kg/m 2 following TIV; Tables 1 and 2) and Pearson's correlation coefficient for correlation analysis (Figure 1). We conducted a paired t-test for paired data (BMI variations from the time of diagnosis to TIV use and from the time of TIV use to the end of follow-up; Table 1). Comparisons between the three groups of communication stages were performed using the one-way analysis of variance (ANOVA; Figures 2-4). To clarify factors related to BMI increase following TIV, we assessed the post-TIV BMI difference by multilevel linear regression analysis, including the BMI as random effects, and the time of assessment as fixed effects (Table 3). We adopted the panel data format in which the same person could appear three to six times (data from 6 years after TIV initiation) to utilize information on cessation cases during follow-up. We calculated the within-subject effect size (estimated regression coefficient divided by estimated level 1 standard deviation) for the BMI value. The effect size was considered low if d-values varied by 0.20, medium at 0.50, and large if greater than 0.80. The model included sex, age at onset, the length of time from onset to TIV use, BMI at TIV use, and communication stage at the end of follow-up as independent variables.
Statistical analysis was two-sided, and the statistical significance was set at p < 0.05. The analyses were performed using JMP ® for Macintosh version 13.0.0 (SAS Institute, Cary, NC, USA), and the multilevel linear regression analysis was conducted using STATA ® version 16.1 (StataCorp, Texas, TX, USA). Informed Consent Statement: Informed consent was obtained from all subjects or their legal guardians involved in the study.
Data Availability Statement: Anonymized data not published within the article will be shared upon reasonable requests from a qualified investigator. The reuse of the data requires permission from the authors.